diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -753,6 +753,7 @@
     'DrydockSSHCommandInterface' => 'applications/drydock/interface/command/DrydockSSHCommandInterface.php',
     'DrydockWebrootInterface' => 'applications/drydock/interface/webroot/DrydockWebrootInterface.php',
     'DrydockWorkingCopyBlueprintImplementation' => 'applications/drydock/blueprint/DrydockWorkingCopyBlueprintImplementation.php',
+    'ExternalSymbolsSource' => 'applications/diffusion/symbol/ExternalSymbolsSource.php',
     'FeedConduitAPIMethod' => 'applications/feed/conduit/FeedConduitAPIMethod.php',
     'FeedPublishConduitAPIMethod' => 'applications/feed/conduit/FeedPublishConduitAPIMethod.php',
     'FeedPublisherHTTPWorker' => 'applications/feed/worker/FeedPublisherHTTPWorker.php',
@@ -2955,6 +2956,7 @@
     'PhortuneSubscriptionWorker' => 'applications/phortune/worker/PhortuneSubscriptionWorker.php',
     'PhortuneTestPaymentProvider' => 'applications/phortune/provider/PhortuneTestPaymentProvider.php',
     'PhortuneWePayPaymentProvider' => 'applications/phortune/provider/PhortuneWePayPaymentProvider.php',
+    'PhpExternalSymbolsSource' => 'applications/diffusion/symbol/PhpExternalSymbolsSource.php',
     'PhragmentBrowseController' => 'applications/phragment/controller/PhragmentBrowseController.php',
     'PhragmentCanCreateCapability' => 'applications/phragment/capability/PhragmentCanCreateCapability.php',
     'PhragmentConduitAPIMethod' => 'applications/phragment/conduit/PhragmentConduitAPIMethod.php',
@@ -3097,6 +3099,7 @@
     'ProjectRemarkupRule' => 'applications/project/remarkup/ProjectRemarkupRule.php',
     'ProjectRemarkupRuleTestCase' => 'applications/project/remarkup/__tests__/ProjectRemarkupRuleTestCase.php',
     'ProjectReplyHandler' => 'applications/project/mail/ProjectReplyHandler.php',
+    'PythonExternalSymbolsSource' => 'applications/diffusion/symbol/PythonExternalSymbolsSource.php',
     'QueryFormattingTestCase' => 'infrastructure/storage/__tests__/QueryFormattingTestCase.php',
     'ReleephAuthorFieldSpecification' => 'applications/releeph/field/specification/ReleephAuthorFieldSpecification.php',
     'ReleephBranch' => 'applications/releeph/storage/ReleephBranch.php',
@@ -6479,6 +6482,7 @@
     'PhortuneSubscriptionWorker' => 'PhabricatorWorker',
     'PhortuneTestPaymentProvider' => 'PhortunePaymentProvider',
     'PhortuneWePayPaymentProvider' => 'PhortunePaymentProvider',
+    'PhpExternalSymbolsSource' => 'ExternalSymbolsSource',
     'PhragmentBrowseController' => 'PhragmentController',
     'PhragmentCanCreateCapability' => 'PhabricatorPolicyCapability',
     'PhragmentConduitAPIMethod' => 'ConduitAPIMethod',
@@ -6663,6 +6667,7 @@
     'ProjectRemarkupRule' => 'PhabricatorObjectRemarkupRule',
     'ProjectRemarkupRuleTestCase' => 'PhabricatorTestCase',
     'ProjectReplyHandler' => 'PhabricatorApplicationTransactionReplyHandler',
+    'PythonExternalSymbolsSource' => 'ExternalSymbolsSource',
     'QueryFormattingTestCase' => 'PhabricatorTestCase',
     'ReleephAuthorFieldSpecification' => 'ReleephFieldSpecification',
     'ReleephBranch' => array(
diff --git a/src/applications/diffusion/controller/DiffusionSymbolController.php b/src/applications/diffusion/controller/DiffusionSymbolController.php
--- a/src/applications/diffusion/controller/DiffusionSymbolController.php
+++ b/src/applications/diffusion/controller/DiffusionSymbolController.php
@@ -47,26 +47,23 @@
 
     $symbols = $query->execute();
 
-    // For PHP builtins, jump to php.net documentation.
     if ($request->getBool('jump') && count($symbols) == 0) {
-      if ($request->getStr('lang', 'php') == 'php') {
-        if ($request->getStr('type', 'function') == 'function') {
-          $functions = get_defined_functions();
-          if (in_array($this->name, $functions['internal'])) {
-            return id(new AphrontRedirectResponse())
-              ->setIsExternal(true)
-              ->setURI('http://www.php.net/function.'.$this->name);
-          }
-        }
-        if ($request->getStr('type', 'class') == 'class') {
-          if (class_exists($this->name, false) ||
-              interface_exists($this->name, false)) {
-            if (id(new ReflectionClass($this->name))->isInternal()) {
-              return id(new AphrontRedirectResponse())
-                ->setIsExternal(true)
-                ->setURI('http://www.php.net/class.'.$this->name);
-            }
-          }
+      $external_sources = id(new PhutilSymbolLoader())
+        ->setAncestorClass('ExternalSymbolsSource')
+        ->loadObjects();
+      $external_sources = msort($external_sources, 'getPriority');
+      $lookup_params = array(
+        'name' => $this->name,
+        'lang' => $request->getStr('lang'),
+        'type' => $request->getStr('type'),
+        'context' => $request->getStr('context'),
+        );
+      foreach ($external_sources as $source) {
+        $uri = $source->lookupSymbol($lookup_params);
+        if ($uri) {
+          return id(new AphrontRedirectResponse())
+            ->setIsExternal(true)
+            ->setURI($uri);
         }
       }
     }
diff --git a/src/applications/diffusion/symbol/ExternalSymbolsSource.php b/src/applications/diffusion/symbol/ExternalSymbolsSource.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/symbol/ExternalSymbolsSource.php
@@ -0,0 +1,20 @@
+<?php
+
+abstract class ExternalSymbolsSource {
+
+  /**
+   * $params may contain:
+   *    - name
+   *    - lang
+   *    - type
+   *    - context
+   * @return string uri to the symbol online docs, or null.
+   */
+  abstract public function lookupSymbol(array $params);
+
+  public function getPriority() {
+    return 500;
+  }
+
+
+}
diff --git a/src/applications/diffusion/symbol/PhpExternalSymbolsSource.php b/src/applications/diffusion/symbol/PhpExternalSymbolsSource.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/symbol/PhpExternalSymbolsSource.php
@@ -0,0 +1,27 @@
+<?php
+
+final class PhpExternalSymbolsSource extends ExternalSymbolsSource {
+
+  public function lookupSymbol(array $params) {
+    if (idx($params, 'lang', 'php') != 'php') {
+      return null;
+    }
+    $name = idx($params, 'name');
+    if (!$name) {
+      return null;
+    }
+    if (idx($params, 'type', 'function') == 'function') {
+      $functions = get_defined_functions();
+      if (in_array($name, $functions['internal'])) {
+        return 'http://www.php.net/function.'.$name;
+      }
+    }
+    if (idx($params, 'type', 'class') == 'class') {
+      if (class_exists($name, false) || interface_exists($name, false)) {
+        if (id(new ReflectionClass($name))->isInternal()) {
+          return 'http://www.php.net/class.'.$name;
+        }
+      }
+    }
+  }
+}
diff --git a/src/applications/diffusion/symbol/PythonExternalSymbolsSource.php b/src/applications/diffusion/symbol/PythonExternalSymbolsSource.php
new file mode 100644
--- /dev/null
+++ b/src/applications/diffusion/symbol/PythonExternalSymbolsSource.php
@@ -0,0 +1,99 @@
+<?php
+
+final class PythonExternalSymbolsSource extends ExternalSymbolsSource {
+
+  public function lookupSymbol(array $params) {
+    if (idx($params, 'lang') != 'py') {
+      return null;
+    }
+    $name = idx($params, 'name');
+    if (!$name) {
+      return null;
+    }
+
+    if (idx($params, 'type') == 'builtin') {
+      if (idx(self::$pyhonBuiltins, $name)) {
+        return 'https://docs.python.org/2/library/functions.html#'.$name;
+      }
+    }
+  }
+
+  private static $pyhonBuiltins = array(
+    '__import__' => true,
+    'abs' => true,
+    'all' => true,
+    'any' => true,
+    'basestring' => true,
+    'bin' => true,
+    'bool' => true,
+    'bytearray' => true,
+    'callable' => true,
+    'chr' => true,
+    'classmethod' => true,
+    'cmp' => true,
+    'compile' => true,
+    'complex' => true,
+    'delattr' => true,
+    'dict' => true,
+    'dir' => true,
+    'divmod' => true,
+    'enumerate' => true,
+    'eval' => true,
+    'execfile' => true,
+    'file' => true,
+    'filter' => true,
+    'float' => true,
+    'format' => true,
+    'frozenset' => true,
+    'getattr' => true,
+    'globals' => true,
+    'hasattr' => true,
+    'hash' => true,
+    'help' => true,
+    'hex' => true,
+    'id' => true,
+    'input' => true,
+    'int' => true,
+    'isinstance' => true,
+    'issubclass' => true,
+    'iter' => true,
+    'len' => true,
+    'list' => true,
+    'locals' => true,
+    'long' => true,
+    'map' => true,
+    'max' => true,
+    'memoryview' => true,
+    'min' => true,
+    'next' => true,
+    'object' => true,
+    'oct' => true,
+    'open' => true,
+    'ord' => true,
+    'pow' => true,
+    'print' => true,
+    'property' => true,
+    'range' => true,
+    'raw_input' => true,
+    'reduce' => true,
+    'reload' => true,
+    'repr' => true,
+    'reversed' => true,
+    'round' => true,
+    'set' => true,
+    'setattr' => true,
+    'slice' => true,
+    'sorted' => true,
+    'staticmethod' => true,
+    'str' => true,
+    'sum' => true,
+    'super' => true,
+    'tuple' => true,
+    'type' => true,
+    'unichr' => true,
+    'unicode' => true,
+    'vars' => true,
+    'xrange' => true,
+    'zip' => true,
+  );
+}